1. Field of the Invention
The invention relates generally to a current-controlled oscillator (CCO), and more particularly, to a current-controlled oscillator that is not affected by process variation, supply voltage variation, and temperature deviation.
2. Description of the Related Art
A current-controlled oscillator is an electronic oscillator designed to generate an oscillation frequency through the control of current. However, similar to most electronic components, the performance of a current-controlled oscillator is often affected by various factors such as process variation, supply voltage variation, and temperature deviation (also called PVT hereinafter). Referring to FIG. 1, an illustrative diagram of a current-controlled oscillator is shown. In FIG. 1, the current-controlled oscillator 10 is designed to generate an oscillation frequency Fout, which may be adjusted by the current source IC. However, although having a fixed current source IC, the oscillation frequency Fout that is output is still varied due to PVT.
FIG. 2 depicts a characteristic curve of a current-controlled oscillator. It is clearly shown in FIG. 2, that the oscillation frequency Fout output from the current-controlled oscillator 10 is inversely related to temperature, which is undesired for an ideal current-controlled oscillator.